Welding apparatus



Jan. 11, 1938. JONES 2,104,749

WEIIJDING APPARATUS Filed Nov. 2, 1955 James l gunes I ATTORNEY Patented Jan; 11, 1938 James L. Jones, Washington, D. C. Application November 2, 1935, Serial uoxiaoei 2G1aims.

(Granted-under as Act of March a, 1883', as amended April so, 1928; 370p. G. 757) This invention relates to welding apparatus, and it has particular relation to apparatus for spot welding a plurality of sheets or plates.

One of the objects of the present invention is a the provision of a welding apparatus by means of which metal plates may be properly welded together regardless of whether they are of varying thickness or whether their surfaces are clean or oxidized.

Another object of the invention is to provide a welding apparatus having means for automatically timing the welding operation in accordance with the temperature of the metal, thus elimihating the possibility of burning the metal by subjecting the same to excess heating, or from obtaining insuiiicient fusion by under-heating the metal, as is frequently the case when the time of weld is determined solely by'the operator. 1

Still another object of the invention is the provision of a welding apparatus which not only includes means for automatically controlling the length of time the welding current is applied to bring the metal up to the proper welding temperature, but also the time that the current is applied thereafter in orderto secure the proper molecular union between the parts.

A further object of the invention is the provision of a welding apparatus embodying the thermocouple controlled bythe temperature of the electrodes for adjustably controlling the time the welding current is applied, in order to bring the work up to the proper temperature for welding and also an. adjustable, slow acting relay controlled by said thermocouple for also controlling the timethe current is applied after the proper temperaturehasbeen reached. I

With these and other objects in view, as well .as other advantages which may be incident to the use of the improvements, the invention consists of the parts and combinations thereof hereinafter set forth and claimed, with the understanding that the several necessary elements constituting the same may be varied in proportion and, arrangement without departing from the nature and scope of the invention, as defined in the appended claims. In order to make the invention more clearly understood, there are shown in the accompanying drawing means for carrying the invention into practical eflect, without limiting the improvemcnts in their useful application to the particular construction, which, for purposes of explanation have been made the subject or illustratlon.

In the accompanying drawing:

Fig. 1 is a diagrammatic view of a welding apparatus constructed in accordance with the invention; I

Fig. 2 is a fragmentary, transverse, sectionai view "through the galvanometer taken on line 22 of Fig, 1;

Fig. 3 isa'perspective view of a welding machine embodying the invention;

Fig. 4 is a longitudinal, sectional view through a welding electrode and associated thermocouple;

Fig. 5 is a view, partly in elevation and partly in longitudinal section, of another form of elec trode and thermocouple;

Fig. 6 is a view partly in elevation and partly in section taken on line.6-6 of Fig. 5;.

Fig. 7 is an elevational view of another attach- Fig. 8 is a similar view of still another form 1' of attachment between the electrode and the elements of the thermocouple; and

9 is a vertical, sectional view of another form of thermocouple in which the elements thereof are heated by the conduction of heat from the work.

Referring to the drawing, a-welding apparatus ;constructed in accordance with the present invention is shown as comprising a pair of welding electrodes l and 2 carried by arms 4 and 4a of a welding machine 40, for movement into and out of welding position with respect to plates 3 and 3a, which are to be spot welded together. Welding current is supplied to the electrodes l and 2 from a transformer l, the primary winding of which is connected with a suitable source of electric energy through wires and 36 and a switch 8, and the secondary winding of which is connected with the electrodes 1 and, 2 through wires 3| and 32, contact 49, armature 41' of an adjustable, slow acting relay 6 of the usual commercial type, and, wire 33 back to the secondary winding of the transformer. The armature 41 is normally maintained in engagement with the contact 49 by means of a coil spring 50, but is moved out of engagement therewith in order to interrupt thewelding circuit by the relay 6 in a manner presently to be described.

The current through the electrodes I and 2 is controlled by a thermocouple comprising members II and H of dissimilar metals, which are secured to the electrode [by screws 9 and I4 and which are connected to the terminals of the coil 48 of a galvanometer 5 by means of wires I and I6. Thegalvanometer 5 includes in its construction a. needle or movable contact member II, which is yieldably held at a zero. position by a spring 52, and which is provided with a contact piece 25 for sliding contact with an ar-' cuatecontact bar 24. The outer end of the needle is insulated from the inner or pivoted end thereof, as at 21, and the contact 24 is also insulated from its mounting, as at 23." The gal- 'vanometer 5 also includes an adjustable contact I8, fixed to a member 20 provided with inwardly tact 24 is connected by a wire 30 with one terminal of the main winding 59 of the relay 5, the other terminal of which is connected by a wire 34 to the wire 35.

As previously stated, the relay 5 is of the slow acting type, in that it is slow to. pick up but quick to release. This action'is effected through a short circuit winding 60, one terminal of which is connected by a wire GI with a. resistance element 52. The other terminal of the winding 60 is connected by a wire 63 to a contact 54, which is' normally engaged by a second armature 55 under the action of a relatively light spring 55; and which is in turn connected by'a wire 61 with a contact 68, mounted for adjustable engagement with the resistance element 52.

. In operation, the switch 8 is first closed so as to complete the circuit through the primary winding of the transformer 'I. The work is then placed between the electrodes land 2 and the latter closed thereon, which completes the circuit from one terminal of the secondary winding of the transformer I, wire 33, armature 41 of relay 5, contact 49, wire 23, electrode i, work 3-3a, electrode 2 and wire 3| back to the other terminal of the secondary winding. The current traversing the circuit justtraced raised the temperature of the metal to the degree required for welding, and also heats the elements l0 and II of the thermocouple. This causes an electric current to flow in the wires I5, l8, .and coil 48 of the galvanometer 5 in the usual manner, and' swings the needle I'I about its pivot in a clockwise direction. 7 When the temperature of the .metal reaches the desired degree, the movable contact I'I engages the contact l8, which is adjust- .ed to such temperature and establishes a. circuit from the line wire through wire 29,adjustable contact I8; movable contacts I! and. 25, fixed contact 24, wire 30, main winding 59 of relay 6 and wire 84 to the line wire 36. The current traversing this circuit energizes the winding 59, but by reason of the fact that the auxiliary winding 68 is shortcirculted, it is slow to attract the armature 41. However, after a given interval of time, which is determined by the adjustment of the contact 58 with respect to the resistance element 82, sufllcient magnetism builds up to attract the armature 41 and open the circuit of the auxiliary winding 50, thereby destroying the neutralizing effect of this winding. This permits the relay 5 to immediately become fully energized and attract the armature 41 against the action of the spring 50, so as to open the contact 49 and the welding circuit controlled thereby.

and is held in adjusted position by- It will bea-pparent from the foregoing that the galvanometer 5 controls the time that the current flows in the welding circuit in bringing the temperature. of the work up to that required fora proper fusion of the parts, and that the slow acting relay 5 controls the timethat the current flows during the actual welding or molecular'union occurs, both of said instrumentalities being adjustable in accordance with the particular metal being united and the thickness and surface characteristics thereof.

If desired, the wires I I and I5 may be connected by wires 54 and 53 with contacts 58, respectively, for engagement by an extension 410 of the armature 41, which is insulated therefrom, as at II. In this case a switch I2 is inserted-in the circuit so as to render this circuit independent from -the thermocouple circuit previously described.

- Fig. 5 illustrates a construction in which the elements III and II of the thermocouple are seemed to the electrode 1 by means of a screw 9{ which engages within the interiorly screw threaded shank 25 of a bolt I4. In this case the shank 25 and the elements I5 and I5 are insulated from the electrode I by a sleeve 5| and washers I2 and I3, respectively of insulating material.

Fig. 8 illustrates a construction in which the elements l0 and II are adjustably secured to the electrode I by means ofa strap 51 and a screw bolt 58. In this case the elements II and I! may be shifted upwardly along the electrode as the latter burns away, by merely loosening the screw bolt 58.

Fig. 9 illustrates a construction in which the wires I5 and I6 are secured to, two semi-cylin drical elements 4| and 42 of dissimilar metals and each provided with a horizontally extending flange 13 at its upper edge. These parts surround the electrode I, being insulated therefrom as at 43, and are yieldably held in contact with the work heated thereby by coil springs 44 interposed between .the flanges I3 and the electrode holder 4. The upper portions of the elements 4 I and 42 and the springs 44 are enclosed within vided, by means of which a very satisfactory welded connection is obtained without danger of under-heating or over-heating the work, and in which the time required for a proper weld is determined automatically in accordance with the type of metal and the thickness of the sheets or plates, as well as the surface characteristics thereof. l I

.Othe'r modifications and changes in' the proportions and arrangement of the parts may be made by those skilled in the art without departing from the nature and scope of the invention, as defined in the appended claims.

The invention described herein may be manufactured and used by or for the Government of the United States of-America for governmental purposes without the payment of any royalties thereon or therefor. What is claimed is:

electrodes; a circuit for supplying electric en- 1. Apparatus for welding comprising a'palr or interval after welding temperature is reached,

2. Apparatus for welding comprising a pair of electrodes; a circuit for supplying electric energy to said'electrodes; a slow acting relay 10 i'or controlling said circuit; a contact device for controlling said relay; and a thermocouple responsive to the temperature of said electrodes for closing said contact device to energize said relay when welding temperature is reached, the v delayed action of said relay interrupting said circuit at a predetermined interval of time after the closing or said contact device 'when the welding operation is completed.

I JAMES L. JONES. 

